A separation membrane module is used in water treatment or gas separation applications which separates a part of components of a mixed fluid. In general, in the separation membrane module, a separation membrane element which is an assembly of a plurality of single separation membranes is housed in a module container. The single separation membrane used in the separation membrane element has various shapes such as a linear shape and a planar shape, and the separation membrane element using a linear single separation membrane is formed such that both end portions of the separation membrane are fixed by membrane bundle fixing materials and both end surfaces of the separation membrane are open to an outside of the membrane bundle fixing material.
For example, in a separation membrane module of Patent Document 1, a hollow-fiber membrane (one type of linear single separation membranes) of a separation membrane element is disposed in a U-shape, and both ends of a membrane bundle thereof are sealed and fixed by a resin wall (an adhesive). Separation is achieved by increasing a pressure of a mixed fluid on an outer diameter side of the hollow-fiber membrane bundle.
When such a separation membrane module is used in a water treatment application for seawater desalination or a gas separation application for separating impurities such as carbon dioxide from natural gas, in order to obtain sufficient membrane separation performance, sometimes the separation membrane module is operated while applying a very high pressure to inside the module.
When the high pressure is applied to the separation membrane module, a very large pressure difference occurs between a portion where the mixed fluid before permeating the separation membrane is present and a portion where permeated components after permeating the separation membrane is present. That is, in the separation membrane module using an external pressure type separation membrane in which the fluid passes from an outer diameter side to an inner diameter side of the hollow-fiber membrane bundle, a part of the components of the mixed fluid permeates into an inner side of the hollow-fiber membrane, and flows from the inner side toward both end opening portions of the hollow-fiber membrane, and hence a force which makes a membrane bundle fixing material having an opening surface of the separation membrane spread out toward both end surfaces of the hollow-fiber membrane is generated. Consequently, the membrane bundle fixing material may sometimes be separated from a module container or the hollow-fiber membrane, or the membrane bundle fixing material may be sometimes broken and the airtightness of the hollow-fiber membrane bundle and the module container may not be ensured. Patent Document 1 describes that a pressure receiving plate is disposed adjacent to the membrane bundle fixing material in order to prevent such deformation of the membrane bundle fixing material.